The present invention relates to connectors and, more particularly, to connectors for high frequency cables.
The invention has for object a connector provided with contacts mounted in an adapted insulator. It is used more particularly in the field of connectors mounted at an end of a cable, to join wires of such cable with contacts contained in the connector, thus allowing a connection with another electronic device, for example, another cable. The invention is applied particularly in the field of connectors for Full Duplex Ethernet cables, this type of cable being used to convey very high frequencies, including the cases in the field of onboard networks, for example in avionics applications. These cables and connectors are designed to be able to convey signals at a frequency of up to about 1 GHz.
The cables are characterized by their characteristic impedance. This characteristic impedance is determined mainly according to the geometry of the cable, as well as according to the materials used to form this cable. The term of geometry covers more particularly the disposition of the wires of the cable inside an insulator of such cable, as well as the respective distances between each of the wires of the cable, and the respective distances between each wire of the cable and a plait of the cable. Namely, the cables generally include a plait surrounding the insulator at an outside periphery, the insulator holding the wires. Besides, the wires of the cable are twisted inside the insulator. This twisted disposition plays also a role in the definition of the characteristic impedance.
In the state of the art, the document FR-A 2 762 453 is known, which teaches a structure of a high frequency electrical connector. This connector includes an insulating body mounted at an outside periphery of the plait of a cable, whereas the connector includes electrical contacts intended to be connected at a first end of the cable wires. However, the cable generally includes several pairs of wires. Therefore, the connector includes several corresponding pairs of contacts. A pair of contacts is arranged in an individual insulating module, so that each insulating module is insulated by means of an individual electromagnetic screen. In such a connector, the wires are untwisted in the region of an intermediate zone in order to be oriented and connected with their respective pair of contacts. In such zone, the characteristic impedance of the cable is modified, merely due to the fact that the cables are untwisted and the relative positions of the wires remain unsecured.
The problem solved by the known documents in the state of the art is to insure a continuity of the screens against electromagnetic interferences likely to be created between the pairs of contacts when these are untwisted and arranged in the connector. In view of this, mainly screening cross-pieces are known which are arranged between each of the insulating modules to separate them from each other. Means to secure the continuity of the characteristic impedance of the cable in the region of the connector are nowhere teached in the state of the art.
The connectors of the state of the art lead to a problem. Namely, the installation of the cable in the connector results in a change of the characteristic impedance of the cable in the region of this connector. The characteristic impedance of the cable being not uniform, a loss in adaptation of the cable is observed.
Particularly when high frequency currents are conveyed by the cable, some losses in the signal are observed, by reflection, because of the variations of the characteristic impedance. In order to be able to guarantee a uniform characteristic impedance along the whole length of the cable, even in the region of the splices, it would be necessary to keep the cable twisted along the whole length thereof. However, this cannot be achieved in the region of the connectors.
An object of the invention is to solve the above problem by providing a connector wherein the cable, while being untwisted, can insure the continuity and the uniformity of the characteristic impedance between the twisted and the untwisted regions of the cable. In this view, the invention provides the use of a quadraxially twisted cable (so-called xe2x80x9cquadxe2x80x9d by the persons skilled in the art) that allows insuring a uniform immunity level, the received perturbations being identical on the different pairs, and because of the symmetrical configuration of the pairs in this type of cable, a differential effect is generated that involves the efficient subtraction of said perturbations. In order to maintain this characteristic, an insulator is provided in the connector, such insulator being able to receive the untwisted wires of the cable and so to insure a characteristic impedance of the untwisted cable, which is very close to the characteristic impedance of the still twisted cable. The insulator of the connector is designed so that the geometry thereof provides channels in which the wires of the cable can be arranged, as well as contacts intended to be connected at the ends of the wires of the cable. Indeed, the geometry of the disposition, such as for example of the relative spacing of the channels, is calculated so that the characteristic impedance of the cable in the region of this insulator is nearly identical to the characteristic impedance before the mounting thereof in the connector. Thus, the invention allows the cable it to keep its characteristics and in particular a characteristic impedance generally uniform, even in the region of the connector.
An object of the invention is a connector including a body to be mounted on a quadriaxially twisted cable, and including at least four contacts and an insulator, such insulator receiving at a first end wires of the cable, and at a second end contact sockets, wherein each wire is able to be connected respectively with one respective socket, characterized in that said insulator includes the channels in which the untwisted wires and the sockets extend, and in that a geometry of the symmetrical disposition of the channels in the insulator is determined according to a characteristic impedance of the cable.